Google collection のMultiSet → 統計処理に便利
Multiset<String> counter = ConcurrentHashMultiset.create();
counter.add("Red");
counter.add("Blue",2);
counter.add("Red",3);
counter.add("Green");
counter.add("Red");
//Set<String> colors = counter.elementSet();
for(Iterator<String> it=counter.elementSet().iterator();it.hasNext();){
String color = it.next();
System.out.println(color+"-->"+counter.count(color));
}